The present invention relates to a driving device for driving an image display element, and particularly relates to a connection mode and signal supply mode of a liquid crystal driver to be mounted as a source driver or gate driver on a liquid crystal module.
The following will describe a system structure of a display driving device of a conventional liquid crystal module referring to FIG. 14.
As shown in FIG. 14, as a driving device for driving source bus lines of a liquid crystal panel 100, there are provided n source drivers S (will be referred to as xe2x80x9cgroup of source drivers Sxe2x80x9d hereinafter where appropriate) which are realized by source driver LSIs (Large Scale Integrated Circuits) each having a bidirectional shift register. The source drivers S are mounted on a liquid crystal panel 100 by being mounted on their corresponding TCP (Tape Carrier Package) 101. The source drivers S are serially connected to one another to supply various signals such as start pulse signal SPD and clock signal CK, which are to be described later.
Each TCP 101 mounting a source driver S is electrically connected to the input terminal (not shown) of the liquid crystal panel 100 by its output terminal for the liquid crystal panel 100, and the input terminal of the TCP is electrically connected to the wiring provided on a print substrate 102, by which the liquid crystal panel 100 and print substrate 102 are electrically connected to each other via the group of source drivers S.
Controller 104 is connected to the print substrate 102 on the side of the source driver S(1). The controller 104 is for supplying control signals and power to the group of source drivers S, and the control signals and power are supplied to each source driver S via wiring on the print substrate 102 and wiring on TCP 101. Note that, although not shown, the controller 104 also supplies control signals and power to a group of gate drivers.
The control signals and power supplied from the controller 104 include: start pulse signal SPD which is in synchronism with a horizontal synchronize signal of a video signal; clock signal CK; video signal Video; switch signal RL for deciding a transfer direction of the start pulse signal SPD in the source drivers S by switching a bidirectional shift register and input/output buffers of each source driver S, and power VCC and GND, etc.
In the structure of FIG. 14, the clock signal CK, video signal Video, switch signal RL, power VCC and GND supplied from the controller 104 are inputted to the first source driver S(1) via input terminal CK1, input terminal Video 1, input terminal RL1, power terminal VCC, and power terminal GND, respectively. By transferring through inner wiring made of, for example, aluminium in the source driver S(1), these signals are then outputted from the source driver S(1) via output terminal CK2, output terminal Video 2, output terminal RL2, output terminal VCC, and output terminal GND, respectively, to be inputted in the same manner to the source driver S(2) of the next stage.
Note that, the supply lines of the signals supplied from the controller 104 may be provided as a common line by the wiring on the print substrate 102 so that the signals are individually inputted to each source driver S.
Meanwhile, as shown in FIG. 14, there are provided two lines for the start pulse signal SPD, one entering the input/output terminal SPD1 of the first source driver S(1), and one entering the input/output terminal SPD2 of the nth source driver S(n), and input is made by selecting one of the lines. By selecting the input/output terminal SPD1 or input/output terminal SPD2 to which the start pulse signal SPD is to be inputted, the transfer direction of the start pulse signal SPD within the group of source drivers S is switched either from the source driver S(1) to the source driver S(n), or from the source driver S(n) to the source driver S(1). This selection of line for inputting the start pulse signal SPD is carried out by the controller 104.
On the start pulse signal output stage of the controller 104, there are provided switches SW1 and SW2 such as analog switches which are switched under the control of control signal SPA (/SPA is an inverted signal of SPA), and selection of line for outputting the start pulse signal SPD is realized by the switching control of the switches SW1 and SW2.
When inputting through input/output terminal SPD1, the control signal SPA is set at xe2x80x9cHighxe2x80x9d level. When the control signal SPA is at xe2x80x9cHighxe2x80x9d level, the switch SW1 on the side of SPD1 is closed, and the switch SW2 on the side of SPD2 is opened. On the other hand, when inputting through input/output terminal SPD2, the control signal SPA is set at xe2x80x9cLowxe2x80x9d level. When the control signal SPA is at xe2x80x9cLowxe2x80x9d level, the switch SW1 on the side of SPD1 is opened, and the switch SW2 on the side of SPD2 is closed.
When the control signal SPA is at xe2x80x9cHighxe2x80x9d level, the start pulse signal SPD is inputted from the input/output terminal SPD1 of the source driver S(1) in synchronism with the clock signal CK, and by transferring through the bidirectional shift register in the source driver S(1), the signal is inputted into the source driver S(2) of the next stage and transferred subsequently to the source driver S(n) of the last stage through the serially connected source drivers S. Here, even though the start pulse signal SPD is outputted from the input/output terminal SPD2 of the source driver S(n) of the last stage, because input is made from SPD1 and the switch SW2 of the controller 104 is open, the start pulse signal SPD is not transferred to the controller 104.
On the other hand, when the control signal SPA is set at xe2x80x9cLowxe2x80x9d level, the start pulse signal SPD is inputted to the input/output terminal SPD2 of the nth source driver S(n), which in this case is on the first stage, and the signal is transferred to the first source driver S(1), which in this case is on the last stage. As with the above case, even though the start pulse signal SPD is outputted from the input/output terminal SPD1 of the source driver S(1) of the last stage, because input is made from SPD2 and the switch SW1 of the controller 104 is open, the signal is not transferred to the controller 104. Further, in this case, the level of switch signal RL for deciding the transfer direction of the start pulse signal SPD in each source driver S is also set inversely.
The following will describe the system structure of FIG. 14 in more detail referring to the block diagram of FIGS. 15(a) and 15(b). In FIGS. 15(a) and 15(b), OS1 to OSm are output terminals to the liquid crystal panel 100 from each source driver S.
In FIG. 15(a), the control signal SPA of the switches SW1 and SW2 in the controller 104 is at xe2x80x9cHighxe2x80x9d level and the switch SW1 on the side of SPD1 is closed. In this state, the start pulse signal SPD is inputted to the input/output terminal SPD1 of the source driver S(1) and it is outputted from the input/output terminal SPD2 to be inputted to the input/output terminal SPD1 of the source driver S(2) on the next stage, and the signal is transferred subsequently in the same manner.
In FIG. 15(b), the level of control signal SPA of the switches SW1 and SW2 and the level of switch signal RL are set inversely, and the transfer direction of the start pulse signal SPD is reversed. That is, in FIG. 15(b), the start pulse signal SPD is inputted from the input/output terminal SPD2 of the nth source driver S(n) and is outputted from the input/output terminal SPD1 to be inputted to the source driver S(nxe2x88x921) of the next stage, and the signal is subsequently transferred to the first source driver S(1) in the same manner.
FIGS. 16(a) and 16(b) show an example in which the line connected to the input/output terminal SPD1 of the source driver S(n) is directly connected to the controller 104 via wiring on TCP 011 and wiring on the print substrate 102 (in FIGS. 15(a) and 15(b), the line connected to the input/output terminal SPD2 of the source driver S(n) is directly connected to the controller 104 via wiring on TCP 101 and wiring on the print substrate 102). FIG. 17 shows a structure of the liquid crystal module corresponding to FIG. 16.
By taking this measure, i.e., by making the transfer direction of the start pulse signal SPD switchable by the bidirectional shift register which is provided as the shift register of each source driver S, the same source drivers S may be provided either on the upper side or lower side of the liquid crystal panel 100, thus reducing the cost of the source drivers S as the driving semiconductor elements.
Further, even when viewed as a liquid crystal module, whether to mount the controller 104 for outputting the start pulse signal on the left or right side of the group of source drivers S can be decided flexibly by making the transfer direction of the start pulse signal switchable, allowing the controller 104 to be provided either on the left side or right side of the group of source drivers S regardless of whether the group of source drivers S are provided on the upper side or lower side of the liquid crystal panel 100, thus making it easier to design a smaller and thinner module.
Further, as shown in FIG. 14 and FIG. 17, the same print substrate 102 can be provided regardless of whether the source drivers S are provided on the upper side or lower side of the liquid crystal panel 100.
However, in recent years, there has been increasing demand for a smaller, thinner, and less expensive liquid crystal module, and effort has been made to meet this demand from a view point of the liquid crystal module as a whole. Therefore, study must focus not only on the source drivers S and gate drivers but also on the controller 104.
As such, to meet such demand, the applicant of the present application sought any possible improvement in the structure of the conventional liquid crystal module, and after extensive research, found that improvements can be made in the following domains.
Namely, in the conventional structure as described above, to enable switching of a transfer direction of the start pulse signal SPD by the bidirectional shift register in the source drivers S, the controller 104 has two lines, one connected to the input/output terminal SPD1 (or input/output terminal SPD2) of the source driver S(1) on the first stage, and one connected to the input/output terminal SPD2 (or input/output terminal SPD1) of the nth source driver S(n). As a result, the number of wires between the controller 104 and the group of source drivers S is increased, and miniaturization of the module is prevented inevitably.
Further, in the described arrangement, input of the start pulse signal SPD is selected by the provision of the switches SW1 and SW2 such as analog switches in the controller 104, which are closed and opened in accordance with control signal SPA. As a result, the structure on the side of the controller 104 is made complex, and because the signals are separately outputted to the side of the input/output terminal SPD1 and to the side of the input/output terminal SPD2 via switches SW1 and SW2, the number of terminals of LSIs on the side of the controller 104 is increased, preventing the size and cost of the controller 104 from being reduced.
Note that, even though the above description is based on the group of source drivers, evidently, the same problems are also presented in a group of gate drivers which drive gate bus lines of a display device.
It is an object of the present invention to provide a display driving device which can reduce the number of terminals of LSIs on the side of a controller, and the number of wires between the controller and a group of driving semiconductor elements, and, in turn, the number of means provided, such as switches, in the controller.
In order to achieve the foregoing object, a display driving device of the present invention includes: a group of driving semiconductor elements including a bidirectional shift register and made up of a plurality of serially connected driving semiconductor elements; and
a single supply line which is branched into two systems for supplying an externally supplied start pulse signal to each driving semiconductor element,
wherein the two systems of the branched single supply line are respectively connected to input terminals of the start pulse signal of driving elements at the both ends of the group of driving semiconductor elements, and
a transfer direction of the start pulse signal is switched with the single supply line by making one of the two systems of the start pulse signal conductive while making the other non-conductive within the group of driving semiconductor elements.
With this arrangement, there is provided only a single supply line for an externally supplied start pulse signal, and this single supply line is branched into two systems to be respectively connected to the input terminals of the start pulse signal of driving semiconductor elements at the both ends of the group of serially connected driving semiconductor elements so as to conduct one of the start pulse signals in the group of driving semiconductor elements.
Thus, it is possible to provide a display driving device which can switch the transfer direction of the start pulse signal without the conventional switching operation between conductive and non-conductive states by the provision of means such as analog switches on the side of the controller which inputs a control signal and other signals to the group of driving semiconductor elements.
Further, by setting a transfer direction of the start pulse signal in accordance with a transfer direction of a data signal, as described above, the same driving semiconductor elements can be mounted either on the upper side or lower side of the liquid crystal panel, and also the controller can be mounted either on the right side or left side of the driving semiconductor elements, regardless of whether the driving semiconductor elements are mounted on the upper side or lower side of the liquid crystal panel. Thus, because one kind of driving semiconductor elements can be positioned variably, the cost of driving semiconductor elements can be reduced.
Further, in this case, because the arrangement in which the transfer direction of the start pulse signal is switchable can be realized with less number of circuits on the side of the controller and less number of semiconductor device terminals to be provided on the side of the controller as compared with the conventional arrangement, the size and cost of the liquid crystal module can be further reduced.
Furthermore, because only a single line is required for the wiring between the controller and the group of driving semiconductor elements, compared with the conventional arrangement in which two lines were provided, in addition to reducing the size of the liquid crystal module, the adverse effect of noise can be reduced by widening the pitch of the wiring pattern which became narrow by the reduction in size of the liquid crystal module. Further, because only a single line is required for the wiring from the controller, there will be no change in wiring pattern due to a positioning relationship between the controller and the group of driving semiconductor elements, thus making designing of the module easier.
In order to achieve the foregoing object, another display driving device of the present invention includes: a single driving semiconductor element including a bidirectional shift register; and
a single supply line which is branched into two systems for supplying an externally supplied start pulse signal to the driving semiconductor element,
wherein the two systems of the branched start pulse signal are respectively connected to input terminals of the start pulse signal at the both ends of the driving semiconductor element, and
a transfer direction of the start pulse signal is switched with the single supply line by making one of the two systems of the start pulse signal conductive while making the other non-conductive within the driving semiconductor element.
Even though the display driving device having the above arrangement incorporates only a single driving semiconductor element, by providing a single supply line for the start pulse signal, the same functions and effects as that of the previously described display driving device having a plurality of driving semiconductor elements can be obtained.
In order to achieve the foregoing object, yet another display driving device of the present invention which is capable of switching a transfer direction of a start pulse signal includes: a group of driving semiconductor elements including a bidirectional shift register and made up of a plurality of serially connected driving semiconductor elements; and
an input/output buffer which is provided for each of input and output terminals of the start pulse signal of each driving semiconductor element, and which is capable of switching input and output by an externally supplied switch signal,
wherein the start pulse signal is supplied to both of connected terminals of an input terminal of the start pulse signal of a driving semiconductor element on a first stage with respect to a transfer direction of a data signal and an output terminal of the start pulse signal of a driving semiconductor element on a last stage with respect to the transfer direction of the data signal, and a signal is prevented from being outputted from the output terminal of the start pulse signal of the driving semiconductor element on the last stage.
With this arrangement, the input terminal of the start pulse signal of the driving semiconductor element on the first stage with respect to the transfer direction of the data signal is connected to the output terminal of the start pulse signal of the driving semiconductor element on the last stage, and the start pulse signal is supplied to both of these connected terminals. In this case, by simply connecting the input terminal of the start pulse signal of the driving semiconductor element on the first stage and the output terminal of the start pulse signal of the driving semiconductor element on the last stage, there occurs a collision of start pulse signals. However, with the described arrangement, this is not a problem since a signal is prevented from being outputted from the input/output buffer of the output terminal of the start pulse signal of the driving semiconductor element on the last stage.
Thus, as with the previously described display driving device, the functions and effects of the single supply line of the start pulse signal can be obtained.
Incidentally, signal output from the output terminal of the start pulse signal of the driving semiconductor element on the last stage can also be prevented, for example, by cutting the output line. However, in such a case, the TCP pattern, etc., may need to be changed when changing the transfer direction of the start pulse signal or depending on the position of the controller with respect to the group of source drivers (group of driving semiconductor elements), and as a result the cost is increased and the convenience of liquid crystal module designing suffers.
Thus, the arrangement in which signal output from the output terminal of the start pulse signal of the driving semiconductor element on the last stage is prevented is preferably arranged such that the output buffer circuit of the input/output buffer of the output terminal sets the output terminal at xe2x80x9cHighxe2x80x9d impedance state. With this arrangement, the operation of the output buffer circuit can be controlled with the use of a power voltage as a set signal of a logic gate provided in the output buffer circuit within the driving semiconductor elements, and thus this arrangement has the following advantages.
First, a xe2x80x9cHighxe2x80x9d impedance state can easily be brought about only by adding a set signal compatible circuit in a conventional input/output buffer. This only results in minute increase in number of circuit elements and can be realized with ease and the chip area will not be increased. Further, because it can be realized only by changing the TCP pattern, only one kind of driving semiconductor element is required, and it is cost efficient. Further, switching can easily be made only by inputting a power (VCC, GND) level, allowing a simple arrangement. Furthermore, because the arrangement can easily be realized by internal circuits without requiring external circuits, it has the advantage of reliability and manufacturing cost.
In order to achieve the foregoing object, still another display driving device of the present invention which is capable of switching a transfer direction of a start pulse signal includes: a single driving semiconductor element including a bidirectional shift register; and
an input/output buffer, which is provided for each of input and output terminals of the start pulse signal of the driving semiconductor element, and which is capable of switching input and output by an externally supplied switch signal,
wherein the input and output terminals of the start pulse signal of the driving semiconductor element are connected to each other, and the start pulse signal is supplied to both of the input and output terminals, and a signal is prevented from being outputted from the input/output buffer of one of the terminals to be an output terminal of the start pulse signal with respect to a transfer direction of a data signal.
Even though the display driving device having the above arrangement incorporates only a single driving semiconductor element, by having the same arrangement as that of the previously described display driving device, the same functions and effects as that of the previously described display driving device can be obtained.
In order to achieve the foregoing object, yet another display driving device of the present invention which is capable of switching a transfer direction of a start pulse signal includes: a group of driving semiconductor elements including a bidirectional shift register and made up of a plurality of serially connected driving semiconductor elements,
wherein two systems of input and output terminals of the start pulse signal are provided for each driving semiconductor element, and
a single supply line for externally supplying the start pulse signal is connected to each of the input terminals of the start pulse signal of driving semiconductor elements at the both ends of the group of driving semiconductor elements by being branched into two systems.
With this arrangement, there are provided two systems of input and output terminals of the start pulse signal for each driving semiconductor element, and a supply line of the start pulse signal is connected to each of the input terminals of the start pulse signal of the driving semiconductor elements at the both ends of the group of serially connected driving semiconductor elements.
Thus, as with the previously described display driving device, the functions and effects of a single supply line of the start pulse signal can be obtained.
Further, with this arrangement, only one of the start pulse signals inputted into the group of driving semiconductor elements from the both ends is conducted, and the output terminal of the driving semiconductor element on the last stage of the transfer direction has an free end, and therefore unlike the previously described display driving device, it is not required to control the operation of the input/output buffer. As a result, it is not required to provide a signal line or other lines for controlling the operation of the input/output buffer, thus making designing of TCP, etc., mounting the driving semiconductor elements easier.
In order to achieve the foregoing object, a display driving device of the present invention which is capable of switching a transfer direction of a start pulse signal includes: a single driving semiconductor element including a bidirectional shift register,
wherein two systems of input and output terminals of the start pulse signal are provided for the driving semiconductor element, and a single supply line for externally supplying the start pulse signal is connected to each of the input terminals of the start pulse signal of the driving semiconductor element by being branched into two systems.
Even though the display driving device having the above arrangement incorporates only a single driving semiconductor element, by having the same arrangement as that of the previously described display driving device, the same functions and effects as that of the previously described display driving device can be obtained.
For a fuller understanding of the nature and advantages of the invention, reference should be made to the ensuing detailed description taken in conjunction with the accompanying drawings.